Cathodes for electron tubes



Sept. 25, 1962 H. LANGER CATHODES FOR ELECTRON TUBES Filed March 25, 1960 FIG?) INVENTOR. HELMUT LANGER FIG. 2

AGENT 3,56,% Patented Sept. 25, 11962 3,tl56,t)6tt CATHGDES FGR ELECTRGN TUBES Helmet Langer, Stamford, Conn., assignor to The Machlett Laboratories, Incorporated, Springdale, Conan, a corporation of (Ionnectieut Filed Mar. 25, 1960, Ser. No. 17,666 8 Claims. (Ql. 313-47! This invention relates to electron discharge devices and has particular reference to novel indirectly heated a relatively short time.

In the operation of electric discharge devices, and particularly electron tubes for high frequency and ultra-high frequency applications, one serious problem is the lengthy warm-up time required to heat the cathode to a temperature suitable for eflicient operation. Conventional tubes employing indirectly heated planar cathodes usually require 40 to 60 seconds warm-up time before the tube can be operated efliciently.

The tube of the present invention is provided with a novel cathode structure which is so constructed and ara relatively expansive area thereof, whereby preoperative warm-up time is reduced to about 10-12 seconds.

It is, accordingly, a primary object of this invention to provide an electron tube with a novel cathode structure which permits eificient operation of the tube after relatively short warm-up periods.

Another object is the provision of a novel cathode structure embodying planar emitter and heater elements so expansive area thereof.

Another object is to provide a cathode structure of the above character which includes a novel baflle structure embodying gettering means located in the areas of the a cathode structure Referring ture shown in FIG. 1 comprises a substantially planar Adjacent the inner surface of the emitter and in predetermined closely spaced relation thereto is a coiled heater an oxide coated surface for The other end of the heater coil forms a leg 19 which extends into one end of a length of metal tubing 20 and into a metal sleeve 21 located within tubing 20. In assembling a heater 9 with the sleeve 21 and tubing 20, the parts are initially assembled in desired relation, with the lower end of sleeve 21 being located at a predetermined known distance from the lower end of tubing 20. With the sleeve in this position and with the heater 9 spaced a proper distance from the adjacent end of tubing 20,

sleeve, so as to hold the leg firmly and immovably in position. In this way the heater 9 becomes fixed at a predeterminecl known distance from the tubing 20.

After the heater unit is assembled, tubing 20 is mounted extending member or pin 22 a disc 23 which extends transversely of and closes inner terminal 15. The spacing between the end of pin 22 and the emitter 10 is a predetermined value. Thus, the engagement of sleeve 21 with pin 22 automatically determines the spacing of the heater 9 from emitter lltl. Terminal 15, disc 23, pin 22, tubing 20, sleeve 21, and leg 19' complete the other side of the circuit to the heater 9.

The emitter Jill is preferably a thin sheet of nickel alloy located about .005" from the heater 9' and having copious electron emission when heated. The heater coils and portions of legs 17 and 19 are preferably coated with aluminum oxide so that the turns of the coil may be closely wound and may actually engage one another without shorting.

To avoid shorting of the heater 9 with emitter 10 under thermal expansion stresses, both are. preferably bowed to a predetermined concavity as shown. Thus, they will remain substantially parallel to each other during operation of the tube. Such concavity of the emitter also causes expansion in a direction toward the heater rather than toward a grid with which the cathode may be used.

It is particularly pointed out that a so-called planar relatively uniformly heated.

Additionally, means is provided in the present structure for efliciently concentrating heat in the area of the emitter. Such means comprises a group of spaced transversely extending disc-like baflles 24, 25 and 26 which are mounted on the end of the tubing 20 adjacent the heater 9. The tubing 26 is provided with a circumferential flange or rim 27 which may be drawn out of the material of the tubing or may be attached to the tubing a short distance from annular spacers 28 between the baffles. of the tubing 20 is flared over as shown to retain the baflle assembly in place.

The baflles are of a diameter nearly approaching the diameter of the heater 9 and thus by reflection efficiently confine heat to the area of the emitter.

The baffle structure possesses additional novelty in that one of the discs, preferably middle disc 25, is made of titanium or other selected gettering material. Since this disc is located in one of the hottest areas of the cathode,

The extreme end at 29 in FIG. 1

it will function as a getter at elevated temperatures which other areas of the structure will not reach.

An additional getter for functioning at lower temperatures is provided by a short length 30 of barium or the like which is affixed to the inner side of foil 12 where it may operate at a predetermined time and temperature by radiation from the heater-bathe assembly.

It will be apparent from the foregoing that an improved cathode structure for an electron tube has been provided which, by more efficient heating of the cathode emitter and concentration of heat at the emitter and by the particular construction and arrangements of the elements accomplishing these improvements, permits the tube to be efficiently operated with relatively short warm-up times.

It is to be understood that modifications may be made in the structures shown and described without departing from the spirit of the invention as expressed in the accompanying claims.

I claim:

1. A quick heating cathode structure for electron tubes, comprising a terminal structure including a pair of hollow cylindrical terminals located in spaced relation one within the other, a tubular support mounted at one end on the terminal structure in conductive relation with the outer terminal, a sealing member within the inner terminal, an axially extending pin fixed at one end to the sealing memher, a disc-like emitter secured at its periphery to the opposite end of the support, a fiat coiled heater closely adjacent the inner side of the emitter and substantially parallel thereto, bafile means disposed adjacent the opposite side of the heater, and a tubular member carrying the battle means and mounted on said pin, one end of the heater being connected to said tubular member and the other end being connected to the outer terminal.

2. A cathode structure substantially as set forth in claim 1 wherein the tubular member has a circumferential flange spaced from its end nearest the heater and against which one side of the bafile means resides, and further has means on its extreme end engaging the opposite side of the battle means for retaining the baffle means in position.

3. A cathode structure substantially as set forth in claim 1 wherein the tubular member contains a sleeve, the adjacent end of the heater is located within the sleeve, and means is provided for rigidly securing the end of the heater, the sleeve, and the tubular member in assembled relation.

4. A cathode structure substantially as set forth in claim 3 wherein said means comprises pressure-induced constrictions in the tubular member and sleeve whereby the assembled parts are frictionally retained in assembled relation.

5. A quick-heating cathode structure for electron tubes, comprising a terminal structure including a pair of hollow cylindrical terminals located in spaced relation one within the other, a tubular support mounted at one end on the terminal structure in conductive relation with the outer terminal, a disc-like emitter secured at its periphery to the opposite end of the tubular support, a sealing member within the inner terminal, an axially extending pin fixed at one end to the sealing member and having its opposite end terminating at a predetermined distance from the emitter, a tubular member mounted upon the pin and containing therein a fixedly located sleeve, a heater located adjacent the emitter and having one end fixed to said sleeve, one end of the sleeve abutting the end of the pin, the spacing between the heater and the abutting end of the sleeve being predtermined whereby when the heater, sleeve and tubular member are assembled as a unit on the pin the heater will be positioned at a predetermined distance from the emitter.

6. A cathode structure for electron tubes, comprising a pair of hollow cylindrical terminals located in spaced relation one within the other, a cylindrical support mounted at one end on the outer terminal, a sealing member within the inner terminal, sealing means between the terminals and insulating one from the other, a disc-like emitter secured to the opposite end of the cylindrical support, a heater adjacent the inner side of the emitter, an elongated member connected at one end to the sealing member and extending axially a predetermined distance toward the emitter, a tubular member telescoped upon and fixed to the. elongated member, and means within the tubular member for limiting the extent to which the tuular member is telescoped onto the elongated member, said means supporting one end of the heater.

7. A cathode structure substantially as set forth in claim 1 wherein the bafile means comprises a group of spaced discs extending transversely of the structure, one of the discs being formed at least in part of a gettering material.

8. A cathode structure substantially as set forth in claim 1 wherein the bafi le means comprises three spaced discs, the middle disc being formed of titanium.

References Cited in the file of this patent 

